Inserting inhibitor to create part boundary isolation during 3D printing

ABSTRACT

A 3D printing system may print a desired 3D object. A fusible powder may fuse when subjected to a fusing condition. A deposition system may deposit portions of the fusible powder on a substrate. A fusing system may apply the fusing condition to the deposited fusible powder. Inhibitor material may not fuse when subjected to the fusing condition. An insertion system may insert a portion of the inhibitor material between portions of the deposited fusible powder after having been deposited by the deposition system, but before being fused by the fusing system, so as to form a boundary that defines at least a portion of a surface of the desired 3D object.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.14/206,762, entitled “INSERTING INHIBITOR TO CREATE PART BOUNDARYISOLATION FOR 3D PRINTING,” filed Mar. 12, 2014; which is based upon andclaims priority to U.S. provisional patent application 61/777,939,entitled “3D PRINTING BY PART BOUNDARY ISOLATION THROUGH POWDER PARTICLEINSERTION,” filed Mar. 12, 2013. The entire content of both applicationsis incorporated herein by reference.

BACKGROUND

Technical Field

This disclosure relates to printers that produce desiredthree-dimensional (3D) objects by fusing deposited powder, including 3Dprinters that use selective inhibition sintering (SIS).

Description of Related Art

Selective inhibition sintering (SIS) may be used to fabricate meso-scalepolymeric and metallic parts. The fabrication may be in layers usingloose powder as the initial material. Polymeric or metallic powder maybe printed in thin layers. After each layer is printed, a liquid may beinkjet-printed on the layer in a pattern that defines the periphery ofthat layer, the interior portion of which may be a layer in a desired 3Dobject. The pattern for each layer may be derived from slices of a 3DCAD model of the object that is to be printed.

The liquid may include an agent that prevents powder particles of basepolymer or metal that have been treated with the liquid from fusing witheach other when heated. The infusible material may define an exteriorsurface of the desired 3D object. The fused material on both sides ofthe unfused material may then be easily separate from one another, thusallowing the desired 3D object to be readily isolated.

The fusible particles may be fused with heat (i.e., sintering). Thesintering may take place after each layer is deposited, such as bypassing a heat radiating device over each layer. All of the layers mayinstead be deposited, each with any needed inhibiting liquid, and theentire loose powder vat may then be sintered at the same time in asintering furnace.

The inhibitor may be a salt solution which leaves particles of saltcrystal in the inhibited regions after water evaporation. In case ofpolymeric part fabrication, these salt crystals may serve to separatethe neighboring base polymer powder material particles and prevent themfrom fusing upon sintering. More details about this and relatedprocesses may be found in U.S. Pat. Nos. 6,589,471, 7,241,415, and7,291,242.

Although SIS technology can be used to fabricate polymeric and metallicparts, in cases of very high temperature sintering it can be difficultto separate adjacent, uninhibited powder regions after they aresintered. Also, the vacuum that may exist when using 3D printing inspace (e.g., on the moon and asteroids) may cause the fluid inhibitor toevaporate, preventing the fluid from inhibiting sintering of areas thatare saturated with the fluid.

SUMMARY

A 3D printing system may print a desired 3D object. A fusible powder mayfuse when subjected to a fusing condition. A deposition system maydeposit portions of the fusible powder on a substrate. A fusing systemmay apply the fusing condition to the deposited fusible powder.Inhibitor material may not fuse when subjected to the fusing condition.An insertion system may insert a portion of the inhibitor materialbetween portions of the deposited fusible powder after having beendeposited by the deposition system, but before being fused by the fusingsystem, so as to form a boundary that defines at least a portion of asurface of the desired 3D object.

The insertion system may include a nozzle that has an interiorpassageway through which the inhibitor material travels. The nozzle mayhave a lower end that includes a leading edge in the shape of a plowthat can plow a trough between portions of the fusible powder when thelower end of the nozzle traverses such portions. The lower end mayinclude a rearward-facing opening though which inhibitor material isejected from the nozzle and into the trough immediately after the troughis plowed by the leading edge, thereby filling the trough as the troughis plowed. The insertion system may cause the leading edge to plowthrough portions of the fusible powder and the opening to ejectinhibitor material from the nozzle immediately after the trough isplowed by the leading edge, thereby filling the trough as the trough isplowed.

The inhibitor material may be a powder. The insertion system may includea vibrating element that controls the flow of the inhibitor powder.

The inhibitor material may be a liquid.

The insertion system may only use the force of gravity to cause theinhibitor material to travel through the passageway and be ejected intothe trough.

The insertion system may include a rotary axis actuator thatcontrollably rotates the leading edge of the nozzle so as cause theleading edge to always be leading the direction of the nozzle movement.

The deposition system may deposit the fusible powder in stacked layers.The insertion system may insert the inhibitor material between theportions of the fusible powder in each stacked layer after thedeposition system deposits the stacked layer into which the inhibitormaterial is inserted and before the deposition system deposits the nextstacked layer.

The insertion system may insert the inhibitor material while the lowerend of the nozzle is moving horizontally and while the lower end of thenozzle is moving vertically.

The insertion system may insert the inhibitor material between portionsof multiple layers of fusible powder, beginning to do so after all ofthe multiple layers have been deposited by the 3D printer.

Guy wires may be attached to the nozzle that prevent the nozzle frombending while the nozzle is moved inside the base powder and inhibitormaterial is being inserted.

The insertion system may include a six-axis gantry control system thatseparately controls six axes of nozzle movement.

The rearward-facing opening may have an adjustable height. The height ofthe rearward-facing opening may be controlled by a movable gate.

The fusing condition may be sintering. The fusible powder may includemetallic powder. The inhibitor material may be a powdered ceramic. Theinhibitor material may include magnesium oxide.

The fusible condition may be exposure to a liquid.

These, as well as other components, steps, features, objects, benefits,and advantages, will now become clear from a review of the followingdetailed description of illustrative embodiments, the accompanyingdrawings, and the claims.

BRIEF DESCRIPTION OF DRAWINGS

The drawings are of illustrative embodiments. They do not illustrate allembodiments. Other embodiments may be used in addition or instead.Details that may be apparent or unnecessary may be omitted to save spaceor for more effective illustration. Some embodiments may be practicedwith additional components or steps and/or without all of the componentsor steps that are illustrated. When the same numeral appears indifferent drawings, it refers to the same or like components or steps.

FIG. 1 illustrates an example of a 3D printing system that creates partboundary isolation during 3D printing by inserting inhibitor material.

FIGS. 2A and 2B illustrate front and rear views of the nozzle that isillustrated in FIG. 1 and that may be used to insert the inhibitormaterial between portions of fusible powder.

FIG. 3 illustrates an example of a desired 3D object being printed withthe 3D printer system illustrated in FIG. 1.

FIG. 4 illustrates the 3D object that has been printed in FIG. 3, afterit is removed from fused material that surrounds it.

FIGS. 5A and 5B illustrate front and rear views of another example of anozzle that may be used to insert inhibitor material between portions ofunfused fusible powder.

FIG. 6 illustrates an example of a desired 3D object being printed withthe nozzle illustrated in FIGS. 5A and 5B.

FIGS. 7A and 7B illustrate front and rear views of another example of anozzle that includes a movable gate that controls the height of arearward-facing opening in the nozzle.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Illustrative embodiments are now described. Other embodiments may beused in addition or instead. Details that may be apparent or unnecessarymay be omitted to save space or for a more effective presentation. Someembodiments may be practiced with additional components or steps and/orwithout all of the components or steps that are described.

FIG. 1 illustrates an example of a 3D printing system that creates partboundary isolation during 3D printing by inserting inhibitor material.The 3D printing system may include fusible powder 101 that fuses whensubjected to a fusing condition; a deposition system that may include apowder spreading roller 103 that deposits portions of the fusible powderin form of a thin layer; a fusing system (not shown) that applies thefusing condition to the deposited fusible powder; inhibitor material 105that may be in a hopper and that does not fuse when subjected to thefusing condition; and an insertion system that inserts a portion of theinhibitor material between portions of the fusible powder after havingbeen deposited by the deposition system, but before the fusing powderbeing fused by the fusing system, so as to form a boundary that definesat least a portion of a surface of the desired 3D object. The infusionsystem may include a nozzle 111, a rotating axis controller 113, agantry system 115, and a controller 117.

The deposition system may deposit the fusible powder 101 in layers orall at once. Examples of a deposition system may be found in U.S. Pat.Nos. 6,589,471, 7,241,415, and 7,291,242.

The fusible powder 101 may include metallic powder material, such asbronze, stainless steel, and/or titanium, or ceramic powder material,such as zirconia, porcelain, and/or a mixture of different ceramics,such as in Lunar soil (regolith) the particles of which may fuse whenheated. The fusible powder 101 may be particulate material mixed with anuncured binder.

The inhibitor material 105 may be a fine dry powder, such as a powderedceramic. The inhibitor material may include magnesium oxide that mayhave a sintering temperature of over 1500 degrees C., and/or ilmenitecommonly found on Moon and Mars.

This fusible powder may be material that can be fused, not by heat, butby water or a fluidic adhesive. For example, powder materials such asplaster or cement which can be consolidated by water may be used as thefusible powder. Correspondingly, ceramic, metallic, and/or any othermaterial that does not react with water may be used as the inhibitormaterial. After delivery of inhibitor material for each layer, the layersurface, including a small amount beyond the boundary, may be sprayedwith water to make up for any inaccuracies in the spray. Aftercompletion of all layers, a cured part may be extracted, while excesscured portions on the outside may fall, as the inhibitor material whichseparates the part from excess cured portions may remain in its unfusedform.

Alternatively, fusible powder may be coated with compound A of athermoset (e.g., epoxy) and the layers may be sprayed by component B ofthe thermoset. The two adhesive compounds may then react and consolidatethe coated fusible powder, while the inhibitor material would only beexposed to compound B and thus may remain unfused.

Inhibitors in liquid or paste forms may be used instead of powder.However, the flow control of inhibitor delivery may be difficult. Unlikethe case of powder, the fluid delivery may have to be pressurized andaccurately regulated.

The rotary axis actuator 113 may controllably rotate a leading edge ofthe nozzle 111, so as to cause the leading edge to always be leading thedirection of the nozzle movement.

The gantry system 115 may controllably cause the nozzle 111 to move todifferent locations while the inhibitor material 105 is inserted betweendeposited fusible powder. The gantry system 115 may move the nozzle 111only horizontally or may also move the nozzle 111 vertically. The gantrysystem 115 may move the nozzle 111 in three dimensional space. This mayenable the inhibitor material 105 to be deposited in any desiredstraight or curved path. The gantry system 115 may provide six axis ofnozzle movement that may be controlled to create inclined layer edges. Atall opening in the nozzle orifice may be used to increase the height ofthe inhibitor material that is inserted.

The controller 117 may be a general or special purpose computerprogrammed to cause the deposition system to deposit the fusible powderat desired locations and in desired amounts, the gantry system 115 toposition the nozzle 111 at desired locations, the nozzle 111 to insertthe inhibitor material 105 at locations within the deposited fusiblepowder that collectively create a portion of a surface of a desired 3Dobject based on a model of the object (such as a CAD model), and thefusion system to fuse the entire mixture, either layer by layer or allat once. The controller 117 may cause the inhibitor material 105 to beinserted in a pattern that demarcates one or more surfaces of the objectto be printed.

FIGS. 2A and 2B illustrate front and rear views of the nozzle 111 thatis illustrated in FIG. 1 and that may be used to insert the inhibitormaterial 105 between portions of fusible powder 101. The nozzle 111 mayhave an interior passageway 201 through which the inhibitor material 105may travel. The nozzle 111 may have a lower end 203 that includes aleading edge 205 in the shape of a plow that can plow a trough betweenportions of the fusible powder when the lower end of the nozzletraverses such portions. The plow may have any profile, such as aprofile that minimizes disturbances to the fusible powder, beyond thewidth of the plow. That profile may be semi-circular, as illustrated inFIGS. 2A and 2B, V-shaped with the vertex of the V facing forward, orotherwise.

The lower end 203 may include a rearward-facing opening 207 though whichinhibitor material can be ejected from the nozzle and into the troughimmediately after the trough is plowed by the leading edge, therebyfilling the trough as the trough is plowed. The insertion system 109 maycause the leading edge 205 to plow through portions of the fusiblepowder. The insertion system 109 may also cause the opening 207 to ejectinhibitor material from the nozzle 111 immediately after the trough isplowed by the leading edge 205, thereby filling the trough as the troughis plowed.

The insertion system 109 may include a vibrating element 209 thatcontrols the flow of the inhibitor material 105 when it is powder. Thevibrating element 209 may include two or more parallel elements that arecaused to controllably vibrate at a high frequency, such as bypiezoelectric disks or by other means. An example of such a vibratingelement is illustrated in U.S. Pat. No. 7,878,789.

The insertion system 109 may only use the force of gravity to cause theinhibitor material 105 to travel through the passageway 201 when it isvibrated and to fall into the trough. The inhibitor material may notfall down without the force of vibration.

While the nozzle 111 is stationary and its lower end 203 is resting onfusible powder, its opening 207 may be blocked by the fusible powder.Thus, the inhibitor material 105 may be blocked from exiting the nozzle111, even when the vibrating element 209 is vibrating. Injection of theinhibitor material 105 may only happen when the vibrating element 209 isvibrating and the nozzle 111 is moving, as the movement of the nozzle111 may create a void in front of the opening 207. The volume of thevoid may opportunistically be filled by the inhibitor material 105. Therate of inhibitor injection may be a function of nozzle speed. The lowerthe speed, the lower the rate of void creation and hence the lower therate of inhibitor material injection. This can provide a self-flowregulation phenomenon that may result in precision deposition ofinhibitor without an elaborate flow controller mechanism.

The fusing system 105 may inject a liquid that cures the uncured binder.The fusing system 105 may instead be a heater that sinters the fusiblepowder. The heating may be generated by resistive heating, microwave, orother heating means that sinters the fusible powder 101, but leaves theinhibitor material 105 intact because of its higher temperaturesintering heat requirement.

After sintering, the final part may be separated from the rest of thesintered material. In case of complex part geometries, separation linesmay be created by the nozzle 111 outside the part geometry, connectingselected points on the layer boundary to the edge of the powder volumeto ease part separation.

FIG. 3 illustrates an example of a desired 3D object 301 being printedwith the 3D printer system illustrated in FIG. 1. The deposition systemmay deposit the fusible powder 101 in stacked layers or all at once. Theinsertion system 109 may insert the inhibitor material 105 between theportions of the fusible powder in each stacked layer after thedeposition system deposits the stacked layer into which the inhibitormaterial 105 is inserted and before the deposition system 10 depositsthe next stacked layer. The fusible powder 101 may be fused after eachlayer is deposited and the inhibitor material 105 is inserted in thelayer, or only after all of the layers and insertions are completed.

FIG. 4 illustrates the 3D object 301 that is being printed in FIG. 3,after it is separated from other fused material that surrounds it.

FIGS. 5A and 5B illustrate front and rear views of another example of anozzle 501 that may be used to insert inhibitor material 105 betweenportions of fusible powder. The nozzle may have a long flute 502. Thinguy wires 503 may be attached to the nozzle 501 to prevent the nozzle501 from bending while the nozzle is moved inside the fusible powder andthe inhibitor material 105 is being inserted. All other aspects of thenozzle 501 may be the same as the nozzle 111. A vibrating element 505may be used and may be the same as the vibrating element 209.

It may be possible to deposit the inhibitor material 105 for an entireset of part layer borders, without progressive layer spreading of thefusible powder 101. This may be done by inserting the nozzle 501 into avolume of fusible powder 101. The lower end of the nozzle 501 can thenbe moved to the bottom layer of the part to be created and movedhorizontally to demarcate the boundary of this layer. The lower end ofthe nozzle 501 may then be elevated to the height of the next layer tocreate an inhibited boundary at the next layer. The cycle may continueuntil the inhibitor powder is deposited for all layer borders. Afterinhibitor deposition is complete, the nozzle may be removed and thepowder vat transferred to a sintering furnace.

Movement of the nozzle and its guy wires inside the loose powder volumemay only disturb the base powder segment that is on top of the layerbeing created and may be above all lower layers as well. Therefore,treated segments of the part under fabrication may remain undisturbed bynozzle movement.

FIG. 6 illustrates an example of a desired 3D object being printed withthe nozzle 501 illustrated in FIGS. 5A and 5B. All of the fusible powder101 may be deposited, either in layers or otherwise, before any of theinhibitor material 105 is inserted. To facilitate this, the nozzle 501and the remaining portions of the insertion system 109 may cause thenozzle 501 to insert inhibitor material 105 into the fusible powder 101while moving horizontally, vertically, in any combination of thesedirections, and at any angle.

FIGS. 7A and 7B illustrate front and rear views of another example of anozzle 701 that may include a movable gate 703 that may control theheight of a rearward-facing opening 705 in the nozzle 701. All otheraspects of the nozzle 701 may be the same as the nozzle 111. To controlthe height of the opening 705, a gate positioning mechanism 707, such asa motor and associate gear, may be used.

Varying the size of the opening 705 may vary the height of the insertedinhibitor material 105. This may be useful during high-speed processing.Thick layers of base material may sometimes be spread and inhibitorborders with higher heights may be delivered. For slant surfaces, asix-axis gantry may be used to provide pitch and yaw orientations forthe nozzle 701, in addition to rotation and XYZ motions.

The 3D printing systems that have been described may be used to printpolymeric, metallic, and ceramic parts, among others. Their uses mayinclude fabrication of parts made of super alloys, ceramic dentalrestorations, and high temperature resistant interlocking ceramic tilesfor lunar and Martian landing pads. Large scale applications may includefabrication of large sand casting molds, building façade structures, andpublic art.

The components, steps, features, objects, benefits, and advantages thathave been discussed are merely illustrative. None of them, nor thediscussions relating to them, are intended to limit the scope ofprotection in any way. Numerous other embodiments are also contemplated.These include embodiments that have fewer, additional, and/or differentcomponents, steps, features, objects, benefits, and advantages. Thesealso include embodiments in which the components and/or steps arearranged and/or ordered differently.

For example, to attain higher density for the final part, each of theinhibitor-inserted layers may be compressed prior to delivery of thesubsequent layer. Alternatively, compression may be applied to the topof the entire powder vat once all layers are spread and inhibitor isinjected for each. The CAD file containing information about the desired3D object may be modified to account for geometrical distortionsresulting from compression.

Unless otherwise stated, all measurements, values, ratings, positions,magnitudes, sizes, and other specifications that are set forth in thisspecification, including in the claims that follow, are approximate, notexact. They are intended to have a reasonable range that is consistentwith the functions to which they relate and with what is customary inthe art to which they pertain.

All articles, patents, patent applications, and other publications thathave been cited in this disclosure are incorporated herein by reference.

The phrase “means for” when used in a claim is intended to and should beinterpreted to embrace the corresponding structures and materials thathave been described and their equivalents. Similarly, the phrase “stepfor” when used in a claim is intended to and should be interpreted toembrace the corresponding acts that have been described and theirequivalents. The absence of these phrases from a claim means that theclaim is not intended to and should not be interpreted to be limited tothese corresponding structures, materials, or acts, or to theirequivalents.

The scope of protection is limited solely by the claims that now follow.That scope is intended and should be interpreted to be as broad as isconsistent with the ordinary meaning of the language that is used in theclaims when interpreted in light of this specification and theprosecution history that follows, except where specific meanings havebeen set forth, and to encompass all structural and functionalequivalents.

Relational terms such as “first” and “second” and the like may be usedsolely to distinguish one entity or action from another, withoutnecessarily requiring or implying any actual relationship or orderbetween them. The terms “comprises,” “comprising,” and any othervariation thereof when used in connection with a list of elements in thespecification or claims are intended to indicate that the list is notexclusive and that other elements may be included. Similarly, an elementpreceded by an “a” or an “an” does not, without further constraints,preclude the existence of additional elements of the identical type.

None of the claims are intended to embrace subject matter that fails tosatisfy the requirement of Sections 101, 102, or 103 of the Patent Act,nor should they be interpreted in such a way. Any unintended coverage ofsuch subject matter is hereby disclaimed. Except as just stated in thisparagraph, nothing that has been stated or illustrated is intended orshould be interpreted to cause a dedication of any component, step,feature, object, benefit, advantage, or equivalent to the public,regardless of whether it is or is not recited in the claims.

The abstract is provided to help the reader quickly ascertain the natureof the technical disclosure. It is submitted with the understanding thatit will not be used to interpret or limit the scope or meaning of theclaims. In addition, various features in the foregoing detaileddescription are grouped together in various embodiments to streamlinethe disclosure. This method of disclosure should not be interpreted asrequiring claimed embodiments to require more features than areexpressly recited in each claim. Rather, as the following claimsreflect, inventive subject matter lies in less than all features of asingle disclosed embodiment. Thus, the following claims are herebyincorporated into the detailed description, with each claim standing onits own as separately claimed subject matter.

The invention claimed is:
 1. A 3D printing system for printing a desired3D object comprising: a deposition system that deposits portions of afirst material on a substrate; an insertion system that inserts aportion of a second material between portions of the deposited firstmaterial after having been deposited by the deposition system; and afusing system that applies a fusing condition to the materials, wherein:the insertion system includes a nozzle that has an interior passagewaythrough which the second material travels; the nozzle has a lower endthat includes: a leading edge in the shape of a plow that can plow atrough between portions of the deposited first material when the lowerend of the nozzle traverses such portions; and a rearward-facing openingthough which the second material can be ejected from the nozzle and intothe trough immediately after the trough is plowed by the leading edge,thereby filling the trough as the trough is plowed; the insertion systemcauses: the leading edge to plow through portions of the first material;and the opening to eject the second material from the nozzle immediatelyafter the trough is plowed by the leading edge, thereby filling thetrough as the trough is plowed; and application of the fusing conditioncauses the desired 3D object to fuse.
 2. The 3D printing system of claim1 further comprising a storage container coupled to the nozzle at an endopposite the lower end, the storage container configured to store apowder or a liquid.
 3. The 3D printing system of claim 2 wherein theinsertion system includes a vibrating element that controls the flow ofthe second material.
 4. The 3D printing system of claim 1 wherein theinsertion system only uses the force of gravity to cause the secondmaterial to travel through the passageway and to be ejected into thetrough.
 5. The 3D printing system of claim 1 wherein the insertionsystem includes rotary axis actuator that controllably rotates theleading edge of the nozzle so as cause the leading edge to always beleading the direction of the nozzle movement.
 6. The 3D printing systemof claim 1 further comprising a controller connected to the depositionsystem and the insertion system, the controller configured to instructthe deposition system to deposit the first material in stacked layers,and instruct the insertion system to insert the second material betweenthe portions of the first material in each stacked layer after thedeposition system deposits the stacked layer into which the secondmaterial is inserted and before the deposition system deposits the nextstacked layer.
 7. The 3D printing system of claim 1 further comprising acontroller connected to the insertion system, the controller configuredto instruct the insertion system to insert the second material while thelower end of the nozzle is moving horizontally and while the lower endof the nozzle is moving vertically.
 8. The 3D printing system of claim 7wherein the controller is further configured to instruct the insertionsystem to insert the second material between portions of multiple layersof the first material, beginning to do so after all of the multiplelayers have been deposited by the 3D printer.
 9. The 3D printing systemof claim 8 further comprising guy wires attached to the nozzle thatprevent the nozzle from bending while the second material is beinginserted.
 10. The 3D printing system of claim 1 wherein the insertionsystem includes a six-axis gantry control system that separatelycontrols six axes of nozzle movement.
 11. The 3D printing system ofclaim 1 wherein the rearward-facing opening has an adjustable height.12. The 3D printing system of claim 11 wherein the height of therearward-facing opening is controlled by a movable gate.
 13. The 3Dprinting system of claim 1 wherein the fusing system is a heater, andwherein the fusing condition is sintering.
 14. The 3D printing system ofclaim 1 wherein the fusing system is a liquid injector, and wherein thefusing condition is exposure to a liquid.
 15. A 3D printing system forprinting a 3D object, comprising: a substrate configured to receive afirst material that fuses when subjected to a fusing condition; a nozzlefor dispensing a second material that does not fuse when subjected tothe fusing condition, the nozzle having an interior passageway throughwhich the second material travels, the nozzle having a lower endincluding a leading edge in the shape of a plow configured to plow atrough between portions of the first material that are not yet fused,and a rearward-facing opening configured to eject the second materialinto the trough after the trough is plowed by the leading edge, therebyfilling the trough with the second material as the trough is plowed; anda rotary axis actuator that controllably rotates the leading edge of thenozzle so as cause the leading edge to always be leading the directionof the nozzle movement.
 16. The 3D printing system of claim 15 furthercomprising a vibrating element configured to control flow of the secondmaterial.
 17. The 3D printing system of claim 15 further comprising adeposition device configured to deposit the first material onto thesubstrate, a fusing device configured to provide the fusing condition,and a gantry device configured to move the nozzle within the firstmaterial.
 18. The 3D printing system of claim 17 further comprising acontroller configured to instruct the deposition device to deposit thefirst material in stacked layers, and instruct the nozzle and gantrydevice to insert the second material within the first material in eachstacked layer and between depositions of the stacked layers by thedeposition device.
 19. The 3D printing system of claim 15 wherein therearward-facing opening has an adjustable height.
 20. A 3D printingsystem for printing a 3D object, comprising: a substrate configured toreceive a first material that fuses when subjected to a fusingcondition; a nozzle for dispensing a second material that does not fusewhen subjected to the fusing condition, the nozzle having an interiorpassageway through which the second material travels, the nozzle havinga lower end including a leading edge in the shape of a plow configuredto plow a trough between portions of the first material that are not yetfused, and a rearward-facing opening configured to eject the secondmaterial into the trough after the trough is plowed by the leading edge,thereby filling the trough with the second material as the trough isplowed; and a deposition device configured to deposit the first materialonto the substrate, a fusing device configured to provide the fusingcondition, and a gantry device configured to move the nozzle within thefirst material.